Can I use the same sending domain with multiple ESPs?
Matthew Whittaker
Co-founder & CTO, Suped
Published 19 May 2025
Updated 15 Aug 2025
7 min read
Many organizations today find themselves using multiple Email Service Providers (ESPs) for different communication needs. For instance, one ESP might handle marketing newsletters, while another manages transactional emails like order confirmations or password resets. A common question that arises is whether it's feasible, or even advisable, to use the same sending domain across all these platforms.
The short answer is yes, you can. However, doing so requires careful configuration and a deep understanding of email authentication protocols to avoid deliverability issues. The goal is to maintain a strong sender reputation across all your sending streams, ensuring your emails reliably reach the inbox.
Navigating this setup effectively means understanding how your domain's DNS records, particularly for SPF, DKIM, and DMARC, interact when managed by different services. It also involves being strategic about subdomain usage and vigilant about monitoring your sending performance.
The mechanics of shared sending domains
From a technical standpoint, using the same root domain with multiple ESPs is entirely possible. The core challenge lies in correctly configuring your DNS records to authorize each ESP to send emails on behalf of your domain. This involves setting up multiple SPF, DKIM, and DMARC records.
For SPF (Sender Policy Framework), you'll need to include all authorized ESPs in a single SPF record for your root domain. If you exceed the 10-lookup limit of SPF, you may encounter what's known as an SPF PermError, which can impact deliverability, especially at Microsoft. One strategy is to use subdomains for different ESPs, allowing for separate SPF records per subdomain. For detailed guidance on SPF, refer to the Postmark SPF guide.
Example DNS records for multiple ESPsDNS
v=spf1 include:esp1.com include:esp2.net -all
esp1._domainkey.yourdomain.com. IN TXT "v=DKIM1; k=rsa; p=PUBLICKEY1"
esp2._domainkey.yourdomain.com. IN TXT "v=DKIM1; k=rsa; p=PUBLICKEY2"
_dmarc.yourdomain.com. IN TXT "v=DMARC1; p=none; ruf=mailto:reports@yourdomain.com; rua=mailto:agg_reports@yourdomain.com"
DKIM (DomainKeys Identified Mail) is handled by adding a unique DKIM record for each ESP. This is usually done by using different DKIM selectors for each ESP, allowing you to have multiple DKIM keys associated with your domain. This setup is crucial for ensuring that each ESP's sending infrastructure is properly authenticated. You can find more information about setting up email authentication for multiple ESPs on the same domain.
Finally, DMARC (Domain-based Message Authentication, Reporting, and Conformance) consolidates the authentication results from SPF and DKIM. You'll typically have one DMARC record for your root domain. DMARC's power lies in its reporting capabilities, allowing you to receive feedback on your sending, whether it's coming from authorized or unauthorized sources. This is essential for monitoring your email ecosystem, particularly when multiple ESPs are involved. You can use DMARC monitoring to track this.
Strategic considerations for multi-ESP environments
The decision to use one sending domain across multiple ESPs often stems from a desire for brand consistency and simplified management. Centralizing your sending under a single domain ensures that all your communications, regardless of their nature (marketing, transactional, support), appear to originate from the same trusted source. This can build stronger brand recognition and recipient trust.
Advantages
Consistent branding: All emails from your organization appear to come from the same trusted domain.
Simplified domain management: You only need to authenticate one root domain, albeit with multiple subdomains and records.
Consolidated reputation (partially): A single domain can build a collective reputation, theoretically benefiting all sending streams.
Disadvantages
Reputation fragmentation: Poor performance from one ESP can negatively impact the entire domain's reputation.
Increased complexity: Managing authentication for multiple ESPs on a single domain is technically demanding.
However, this approach isn't without its caveats. While the primary domain offers a unified brand presence, the underlying technical infrastructure and sending practices of each ESP play a significant role. If one ESP has poor sending practices or is used for risky mail streams, it can negatively affect the reputation of your entire domain, potentially impacting deliverability from all your ESPs. This is a key reason why many choose to segment their sending more rigorously.
It's also important to understand the concept of reputation risk when using the same sending domain on multiple platforms. Each platform's sending IP addresses contribute to a different aspect of your sending identity. While the domain provides overarching branding, the specific IPs and subdomains used by each ESP will also develop their own reputations with ISPs.
Navigating reputation and deliverability challenges
A significant challenge in using a single domain across multiple ESPs is managing sender reputation. Internet Service Providers (ISPs) track various metrics, including spam complaints, bounce rates, and engagement, to assess the trustworthiness of a sending domain. When multiple ESPs use the same domain, a poor performance from one can trigger negative signals for the entire domain. This can lead to reduced inbox placement, increased spam folder delivery, or even a domain blocklist (or blacklist) listing.
The impact of reputation fragmentation
Even with proper DNS authentication, ISPs still evaluate each sending stream independently to some extent. If your transactional ESP maintains excellent engagement while your marketing ESP experiences high complaint rates due to aggressive sending, the latter's negative impact can spill over, affecting the deliverability of your critical transactional emails. This is a key deliverability risk of using multiple ESPs.
Another concern is blocklisting. If one ESP's shared IP address or a specific sending practice used by one of your mail streams gets your domain on a blocklist, it can prevent all emails sent from that domain, regardless of the ESP, from reaching recipients. This makes blocklist monitoring essential. For a deeper dive into how blocklists operate, explore our guide to email blocklists.
To mitigate these risks, it is critical to segment your email traffic effectively and maintain high deliverability standards across all ESPs. This includes managing your mailing lists, avoiding sending to unengaged recipients, and ensuring proper unsubscribe processes are in place for every sending stream.
Best practices for robust configurations
When deploying a multi-ESP strategy with a single sending domain, adherence to best practices is paramount. The primary recommendation is to use distinct subdomains for each ESP. For example, marketing.yourdomain.com for one ESP and transactional.yourdomain.com for another. This practice helps segregate reputation, so issues with one sending stream are less likely to impact others. The M3AAWG Sending Domains Best Common Practices further elaborates on this.
Authentication Type
Configuration for Multiple ESPs
Impact on Deliverability
SPF
Include all ESPs in one SPF record for root domain, or use subdomains.
Prevents spoofing and identifies authorized senders.
DKIM
Each ESP gets its own unique DKIM record (selector).
Verifies email content integrity and sender identity.
DMARC
Single record for root domain, reports on all sending.
Enforces alignment and provides visibility into all email traffic.
When transitioning or onboarding a new ESP, always plan for IP and domain warming. Even with an established domain, a new ESP will be sending from new IPs, which need to build their own reputation. A gradual ramp-up of sending volume through the new ESP is essential to avoid being flagged as suspicious by ISPs. It's also wise to check if you should use the same or different subdomains for multiple ESPs.
Communication with your ESPs is key. Inform them of your multi-platform strategy. They can provide specific DNS records and guidance tailored to their infrastructure. Regularly review your DMARC reports to identify any authentication failures or unauthorized sending activity from any of your ESPs, which will help you maintain a clean sending record and quickly address any emerging issues.
Conclusion
Using the same sending domain with multiple ESPs is technically viable and can offer brand consistency, but it demands meticulous planning and ongoing management. Proper configuration of SPF, DKIM, and DMARC, coupled with strategic subdomain usage and vigilant monitoring, will help you maintain a healthy sender reputation and ensure high deliverability across all your email programs.
Views from the trenches
Best practices
Always use distinct subdomains for each ESP to segment reputation, like marketing.yourdomain.com and transactional.yourdomain.com.
Ensure SPF records for your main domain include all authorized ESPs, but be mindful of the 10-lookup limit to avoid errors.
Implement unique DKIM selectors for each ESP to allow for separate authentication keys tied to your domain.
Leverage DMARC reports to gain full visibility into all email sending from your domain and quickly identify issues.
Communicate openly with your ESPs about your multi-platform sending strategy to get tailored support and guidance.
Common pitfalls
Failing to use separate subdomains, which can lead to reputation fragmentation and deliverability issues across all streams.
Exceeding the SPF 10-lookup limit, causing SPF PermErrors that can lead to emails landing in spam or being rejected.
Not configuring unique DKIM records for each ESP, resulting in authentication failures and reduced trust.
Ignoring DMARC reports, which means missing critical insights into unauthorized sending or authentication problems.
Rapidly increasing sending volume on a new ESP without proper IP warming, triggering spam filters.
Expert tips
Consider a DMARC policy of p=quarantine or p=reject for enhanced protection, but transition carefully.
Regularly monitor your domain's health using Google Postmaster Tools and other reputation monitoring services.
Ensure your email lists are clean and engaged to minimize bounces and spam complaints across all platforms.
Implement consistent sender names and branding across all ESPs to reinforce recipient trust.
Use clear, standardized naming conventions for your subdomains to easily identify each ESP's traffic.
Expert view
Expert from Email Geeks says you can use the same domain, but you cannot use the exact same subdomain in the RFC 5321.From address because that address needs to be specific to the ESP handling bounces.
2021-02-19 - Email Geeks
Expert view
Expert from Email Geeks says different selectors should be used for the d= value in the DKIM records.
Microsoft. One strategy is to use subdomains for different ESPs, allowing for separate SPF records per subdomain. For detailed guidance on SPF, refer to the Postmark SPF guide.
ESPs in one SPF record for root domain, or use subdomains.
ESP gets its own unique DKIM record (selector).
